Add manual sync API and bichonsync CLI

[azure9]

Summary

• Add a new sync module with REST API endpoints for on-demand IMAP sync, single-folder gap-aware sync, mailbox status inspection, sync verification, and raw EML fetching
• Add bichonsync CLI binary for manual sync controls against the Bichon API
• Extend EnvelopeIndexManager and EmlIndexManager with flush(), count_messages_in_mailbox(), and get_all_uids() methods

New API Endpoints

Method	Path	Description
POST	/api/v1/sync/:account_id	Trigger on-demand full sync for an IMAP account
POST	/api/v1/sync/:account_id/:mailbox_id	Gap-aware single folder sync (compares all server UIDs vs local, fetches missing)
GET	/api/v1/sync/mailbox-status/:account_id	Offline mailbox status with server vs local message counts
GET	/api/v1/sync/verify/:account_id	Verify sync completeness against the IMAP server (detects missing folders and messages)
POST	/api/v1/sync/:account_id/:mailbox_id/fetch-eml	Fetch raw EML content for specific UIDs from IMAP (base64 encoded, without storing)

bichonsync CLI Commands

Command	Description
list-accounts	List all accounts
list-mailboxes -a <id>	List mailboxes with server/local counts and sync status
sync -a <id>	Trigger full account sync
sync-folder -a <id> -m <id> [--export-dupes]	Sync single folder; optionally export missing/duplicate messages as .eml files
verify -a <id>	Verify sync completeness (remote vs local)

Key Implementation Details

• Gap-aware sync: perform_single_folder_sync compares the full set of server UIDs against local UIDs (via new get_all_uids()), fetching only the delta — unlike perform_incremental_sync which only looks at UIDs above the local max
• Index flush: Added a Flush variant to WriteMessage with a oneshot channel to synchronously commit pending writes, ensuring accurate counts immediately after sync
• EML export: The --export-dupes flag on sync-folder fetches raw email bodies via IMAP BODY.PEEK[] and saves them to a temp directory, useful for debugging duplicate/missing messages
• RFC 2047 decoding: Included a decode_rfc2047 helper for readable subject lines in the missing-messages report

Files Changed

File	Change
Cargo.toml	Register bichonsync binary
src/bin/bichonsync.rs	New — CLI tool (539 lines)
src/modules/sync/mod.rs	New — Sync service logic (486 lines)
src/modules/rest/api/sync.rs	New — API endpoints (139 lines)
src/modules/rest/api/mod.rs	Register SyncApi tag and endpoints
src/modules/indexer/manager.rs	Add flush(), count_messages_in_mailbox(), get_all_uids(), Flush message variant
src/modules/cache/imap/sync/flow.rs	Make perform_incremental_sync public
src/modules/mod.rs	Add pub mod sync